Floating shock absorber



NGV i2, 1946 N. o. MYKLESTAD FLOATING SHOCK ABSORBER Filed Nov. 27, 1944JNToR. M0. Jil/@57740 ArroQA/fy l...`..,.n..r.,r lauw?....If........fuLL-{Eil.Kill l.. |I||||| :I IIIIIII IIIGIIIIII.

Patented Nov. 12, 1946 v-oNlTlszo STATES PATENT OFFICE i Nils o.Myklestad, Pasadena, Calif.

Application November 27, 1944, Serial No. 565,313

6 Claims.

This invention relates to improvements in shock absorbers. In theconventional shock absorber there is a piston and a cylinder that areconnected to two relatively movable parts such as for example, therunning gear and the frame of a vehicle. When relative movement betweenthese parts occurs the piston forces a uid such as a light oil through astationary stricture or orice and the resistance of the fluid to beingforced through the stricture offers the retarding effort that resists orretards relative movement between the parts. An objection to such aconstruction resides in the fact that the stricture or orifice when itis stationarily positioned can and will offer the maximum resistance tothe passage of oil therethrough depending upon the velocity with whichthe movable parts move relatively to each other. Thus, ifthe piston isurged to move relatively toA the cylinder suddenly or withr highvelocity a maximum retarding effect is immediately effective to resistrelative movement. It is only when the piston and cylinder moverelatively to each other at a slow velocity that the retarding effortcreated by the stricture is reduced.

An object of the present invention is to provide an improved shockabsorber wherein the stricture or orice is movably mounted and has itsmovement in turn retarded by springs. rangement the effect of thestricture in retarding relative movement between the piston and cylinderis somewhat delayed in that if the piston moves relatively to thecylinder suddenly or with high velocity *thek stricture-providing meansis' bodily shiftedunder the eiiect of the fluid and is directly opposedin its movement by the springs. In this way during a stroke ofv thepiston relatively to the cylinder the movement if sudden, is at "iirstspring-opposed and the retarding effect ofthe stricture increases indirect proportion to the compression of the spring. Consequently withthis delayed action or built-up action severe shocks are not transmittedto the frame of the vehicle andthe life ofthe vehicle is materiallyprolonged with smoother riding obtained. j

Another object oi the invention is to provide a shock absorber havingthe above-mentioned characteristics wherein a limited amount of lostmotion or loose play is present between the piston rod and its pistonsuch loose play permitting small movements of the piston rod relativelyto the cylinder without causing any shock absorbing action to take placewhatsoever. Thus, where there may be a `multiplicity of small vibrationsof low amplitude but of high velocity these vi- With this ar -brationsbecause of their low amplitude are not tailed description andspecifically pointed out in the appended claims, reference is had to theaecompanying drawing for an illustrative embodiment of the invention,wherein:

Figure 1 is a diametrically vertical section through the shock absorberembodying the present invention illustrating the shock absorber in whatmay be regarded as a normal or neutral position;

Fig. 2 is a view similar to Fig. 1, but illustrating the positionassumed by the parts at or near the end of a long downward stroke of thepiston; Fig.Y 3 is a horizontal section taken substantially upon theline 3--3 upon Fig. 1;

Fig. 4 is a horizontal section taken substantially upon the line 1l-4upon Fig. 1; and

Fig. 5 is a partial View in vertical section illustrating details of amodied or alternative `form of construction.

Referring to the accompanying drawing wherein similar referencecharacters designate similar parts throughout, the improved shockabsorber comprising a body generally indicated at I0 providing inner andouter concentrically arranged cylinders I'I and I2 closed at their endsby end closures or caps I3 and I4.

Within the inner cylinder II there is disposed a piston I5 through whichextendsa port I6 that is adapted lto be closed by an upwardly closingcheck valve II. The piston is also provided with ports I8 `which openupwardly to the interior of the inner cylinder Il.Y The piston isadapted to be ractuated within its cylinder by a tubular piston rod 2l!having a head I9 in which there are ports 2l. The head1-9 fits with aconsiderable verticalclearance within the piston I5 so that there is asubstantial amount of vertical lost motion or relative movementpermissible between the piston rod and the piston which is effective toopen and close the ports 2|. Thus, as illustrated in Fig'. 2,whereinsthe piston rod 20 is in its' lowermost position relative to thepiston, ports 2I are fully open. In Fig; r1 these ports are illustratedas partially closed and when the tubular piston rod 20 is in itsuppermost position relatively to the piston, ports 2l are fully closedby the surrounding structure of the piston.

The upper endof the piston rod extends into an air chamber or reservoir22 which may be equipped with a filler plug 23 for replenishing the oilor other fluid in the shock absorber. The interior of this air chamberor reservoir is in communication with the hollow piston rod by means ofports 24 and the oil level therein is normally maintained at orapproximately even with these ports so that there is a substantialvolume of air in the air chamber above the oil therein. 25 indicates anapron that may be secured to the air chamber and which telescopicallyextends downwardly over the body IU. Knuckles 26 and 21 may be providedon the air chamber 22 and cn the lower end closure, respectively, toprovide means for attachment of the shock absorber to two relativemovingparts, such as for example the running gear and the frame, respectivelyof a vehicle. In the top and bottom of the inner cylinder II there areports 28 and 29, respectively, which establish communication between theinner cylinder II and the outer cylinder I2. AIn the outer cylinderthere is a recprocable sleeve or bushing 3E! in which strictures 3| areformed. These strictures may be in the nature of a plurality oflongitudinally extending small holes or they may be so formed as toprovide narrow orifices indicated at- 32. Spacer rings 33 and 34 arepositioned against the top and bottom of the sleeve 3G, respectively,and provide spring seats for helical compression springs 35 and 36.These spacer rings are preferably externally recessed or notched so thatoil can not become entrapped between the sleeve or bushing and outercylinder I2 when the spacer rings are displaced upwardly or downwardlyas the case may be from a position shown in Fig. l Ato a Vposition suchas is illustrated in Fig. 2. The lower compression spring 36 has itslower end seated against the bottom closure I4 while the upper end ofthe compression spring 35 is seated against a spacer ring 3l. A heavycompression spring 38 is seated on spacer ring 31 and has its upper endseated against the top closure I3. The spacer rings V33 and 34 arelimited in their movements toward each other by internal shouli dersformed on the interior of the outer cylinder l2, the lower spacer ringbeing illustrated as seated against its shoulder in Fig. 2. Thecompression springs are preferably given some initial compression, or inother words, they are pre-stressed when the structure is assembled'together so that a finite force is required to force sleeve 3i) from itsneutral position and further compress one of these springs.

The operation of the shock absorber is substantially as follows: If thevibration or movements of the piston rod 2!) relative to cylinder I Ido'not exceed lthe length of the stroke permissible between the 4head I9and the piston, the piston rod and cylinder may readily vibraterelatively to each other without shifting the piston I and withoutbringing into play or operation the effects of the strictures 32 or ofthe springs 35 and 33. During such conditions of operation no power isabsorbed or consumed. Where the vibration between the piston rod 2B andthe cylinder II exceeds in amplitude the length of the strokepermissible between head I9 and piston I5, this vibration ifV at veryslow velocity may expel oil from cylinder II into the Outer cylinder I2and the oil may be caused to flow through the strictures 32 in sleeve 30as long as the total pressure diierence on the two ends of sleeve 38 isless than the initial spring force holding the sleeve in its central orneutral position. If the movement of the piston rod 20 relatively to thecylinder II is at low frequency but high amplitude, such as is the casewhen the body of the vehicle vibrates at one of its natural frequencieson its springs, the oil will be expelled from cylinder II at such a highvelocity that it can not be crowded through the strictures 32 fastenough. Under .these circumstances, a pressure differential is placed onopposite ends of sleeve 30 and the sleeve is forced against one of thecompressed springs. Thus, as illustrated in Fig, 2, the sleeve 30 hasbeen forced upwardly due to a powerful downward stroke of piston rod 20.When such action takes place the damping or retarding force is acombination of the resistance afforded by the strictures 32 and thespring or springs tending to return the sleeve-to its central or neutralposition illustrated in Fig. 1. Later in the stroke, particularly asVibratory velocity diminishes, any spring that has been compressed willagain extend and may return the sleeve 30 to its neutral position beforethe piston reaches the end of its stroke. If the springs are maderelatively stiif and the strictures 32 quite narrow a large amount ofenergy can be absorbed per stroke in this manner. It will, of course beappreciated that upon a change of direction of stroke of the piston rod2 relative to cylinder II that the initial movement or beginning of thechanged stroke is not retarded whatsoever because of the lost motionbetween head I9 and piston I5. As soon as this lost motion is taken upthe retarding effort or damping eiect quickly builds up an equilibriumcondition whereas the force of the oil that is being crowded through thestrictures 32 is opposed by the expansive eiorts of the compressedspring or springs. This building up of the retarding effort, asdistinguished from its becoming immediately eifective which would be thecase if the strictures were stationary, reduces the transmission ofshocks to the frame of the vehicle, thus promoting longer life for thevehicle and contributing to easier riding. Also, when the amplitude ofthe vibratory motion is large the length of stroke necessary to take upthe lost motion becomes only a small fraction of the total stroke, Ifvthe movement of the piston rod relatively to the cylinder is at highvelocity the oil will be expelled from cylinder I I at such a rate thatonly a small part of it can be crowded through the strictures 32 as longas the amplitude of motion is small enough so as to not compress thesprings with great force. Due to the rapid compression of the stroke incases of high frequency most of the extension of the spring will takeplace at the beginning of the return stroke thereby delaying the lostmotion between piston l5 and piston rod 2U. In this way, only a smallamount of energy will be absorbed by the shock absorber under theseconditions which is highly desirable. On avery bumpy road, however, themovement of the piston rod relatively to the cylinder may be both veryrapid and also. of large amplitude such as is occasioned by a series ofsevere shocks. Again it becomes, necessary for the shock absorber toabsorb a large amount of energy in order to prevent large .vibratorymotions of thevehicle. Under these cir.- cumstances, the veryv heavyspring `38 isA utilized and as this spring is capable of asserting avery great force the oil is forced through the strictures 32 with veryhigh velocity before the long rapid stroke can be completed, In thisway, a large amount of energy can be absorbed before any sudden shockwhatsoever is transmitted to the vehicle. It will, of course, beappreciated that if no oil whatsoever flows through the strictures thesprings would be fully compressed for a motion of the piston rodrelatively to the cylinder of only about one-half of the maximumpermissible motion. This insures that for large amplitudes of vibratorymotion a large amount of oil must always flow through the stricturesthereby exerting a powerful damping influence when it is most needed.For small amplitudes of motion on the other hand, damping is undesirableand under these conditions the spring force will not increase to such amagnitude that a large amount of oil is forced through the strictures.

In Fig. 5, I have illustrated a modified form of construction whereinthe head ma has formed therethrough small passages di) arranged inalignment with the ports Ita. The check valve lla has one or more smallpassages i! formed therein. In this form of construction the sleeveutilized does not have any passages or strictures therethrough butprovides a movable but impervious barrier between the top and bottom ofthe outer cylinder l2. In this form of construction during downwardstrokes check valve lla will, of course, close and the sleeve may or maynot be forced upwardly against the upper springs. The oil is crowded orforced through the apertures M into the tubular piston rod. Conversely,on upward strokes oil in the inner cylinder l I may be forced downwardlythrough passages El and its pressure may or may not be effective toforce sleeve 3@ downwardly within the outer cylinder l2. In this form ofconstruction there are the same advantages previously described andexplained except that the oil, instead of being forced throughstrictures in the sleeve is forced through corresponding passages in thehead ma, and the check valve lla, respectively.

Various changes .may be made in the details of construction withoutdeparting from the spirit and scope of the invention as dened by theappended claims.

I claim:

l. A shock absorber comprising means providing two concentric cylinderscommunicating with each other at their ends, a piston reciprocablewithin the inner cylinder, a sleeve movably fitting in the outercylinder, strictures formed in the sleeve restricting flow therethrough,and means for retarding movements of the sleeve,

2. A shock absorber comprising concentric cylinders in communicationwith each other at their ends, a piston reciprocable within the innercylinder, a sleeve having strictures therethrough, reciprocable in theouter cylinder, and spring means in the outerl cylinder urging thesleeve into a neutral or normal position.

3. A shock absorber comprising means providing a pair of concentriccylinders, a piston reciprocable in the inner cylinder, a piston rodextending into the inner cylinder and operatively connected to saidpiston to reciprocate it, a stricture-providing means reciprocable inthe outer cylinder, and spring means urging said stricture-providingmeans into a neutral or central position.

4. A shock absorber comprising means providing a pair of concentriccylinders, a piston reciprocable in the inner cylinder, a piston rod eX-tending into the inner cylinder and operatively connected to said pistonto reciprocate it, a stricture-providing means reciprocable in the outercylinder, and spring means urging said strictureproviding means into aneutral or central position, there being a loose play between the pistonrod and the piston and for the purpose described.

5. A shock absorber comprising means providing a pair of concentriccylinders, a piston reciprocable in the inner cylinder, a piston rodextending into the inner cylinder and operatively connected to saidpiston to reciprocate it, a stricture-providing means reciprocable inthe outer cylinder, spring means urging said stricture-providing meansinto a neutral or central position, said piston having passagestherethrough, a check valve preventing flow through the piston in onedirection, and means on the piston rod for opening and closing passagesthrough the piston rod against flow therethrough in the other direction.

6. A shock absorber comprising means providing a pair of ,concentriccylinders, a piston reciprocable in the inner cylinder, a piston rodextending into the inner cylinder and operatively connected to saidpiston to reciprocate it, a stricture-providing means reciprocable inthe outer cylinder, spring means urging said stricture-providing meansinto a neutral or central position, said piston having passagestherethrough, a check valve preventing iiow through the piston in onedirection, and means on the piston rod for opening and closing passagesthrough the piston rod against flow therethrough in the other directionsaid pi-ston rod being hollow and an air chamber in communicationtherewith.

N. O. MYKLESTAD.

